Alright, I thought I’d do a quick blog on the DNS or the Domain Name Service? Why? Well because without it the Internet as we know it would not work and subversion of the DNS system is how Turkey recently blocked access to Twitter, Facebook and YouTube so it’s very topical!

First off you need to know that every computer connected to the Internet has a unique numeric address, kinda like a phone number. For example the server that Google runs on (at least one of them) has an address of 74.125.237.114. If you type that into your browser’s address bar you will see the Google search page!

Now, in the real world, it’s very hard to remember more then a few phone numbers, so we use phonebooks, like the white and yellow pages, to make it easy to look up a phone number. This is basically what the DNS is, the phonebook of the Internet. When you type in www.google.com into your browser, your computer uses the DNS to figure out that the address of the computer you want to connect with is 74.125.237.114 !

This fun video explains things in more detail:

So how did Turkey block Twitter, Facebook and YouTube? Well, initially they forced the Turkish ISPs to change their DNS servers to provide the “wrong” address for the Twitter, Facebook and Youtube’s servers. This meant that a person connected to the Internet in Turkey who tried to access these sites saw some kind of government site instead.

People quickly clicked as to what was happening and spread the word to configure their computers to not use their ISP’s DNS servers but to instead use Google’s servers (at 8.8.8.8). In fact this information started to appear as graffiti on walls and posters in Istanbul:

Source http://mashable.com/2014/03/21/twitter-ban-turkey-graffiti/

This worked for a while until the Government got wise and forced the ISPs to block traffic to 8.8.8.8 and 8.8.4.4, effectively cutting off access to the Google DNS servers.

Still as John Gilmore famously said: “The Net interprets censorship as damage and routes around it” and by using virtual private networks (VPNs) and censorship resistant networks such as Tor the people of Turkey were still able to connect to Twitter, Facebook and Youtube to air their views about their government.